code: def test_diff_without_targets_specified(tmp_dir, dvc, scm, file):
      params_file = tmp_dir / file
      params_file.dump({"foo": {"bar": "bar"}, "x": "0"})
      dvc.stage.add(
          name="test",
          cmd=f"echo {file}",
          params=[{file: None}],
      )
      scm.add_commit([params_file, "dvc.yaml"], message="foo")
  
      params_file.dump({"foo": {"bar": "baz"}, "y": "100"})
      assert dvc.params.diff() == {
          "diff": {
              file: {
                  "foo.bar": {"new": "baz", "old": "bar"},
                  "x": {"new": None, "old": "0"},
                  "y": {"new": "100", "old": None},
              }
          }
      }
  
file_path: dvc/tests/func/params/test_diff.py
imports: from os.path import join
  import pytest
  from dvc.utils import relpath
label_desc: Use image node_id 14 for calling a global function with example usage: test_diff_without_targets_specified(tmp_dir, dvc, scm, file) without return types